解题方法
1 . (1)如图1,点A在直线l外,仅利用圆规和无刻度直尺,作直线
(保留作图痕迹,不需说明作图步骤).
(2)证明:一簇平行直线被椭圆所截弦的中点的轨迹是一条线段(不含端点);
(3)如图2是一个椭圆C,仅利用圆规和无刻度直尺,作出C的两个焦点,简要说明作图步骤(只说明作图步骤).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7d63989923cff8efb6d67070be48794.png)
(2)证明:一簇平行直线被椭圆所截弦的中点的轨迹是一条线段(不含端点);
(3)如图2是一个椭圆C,仅利用圆规和无刻度直尺,作出C的两个焦点,简要说明作图步骤(只说明作图步骤).
![](https://img.xkw.com/dksih/QBM/editorImg/2024/1/9/1cc29044-247d-4d10-a2ed-edcd5f41007d.png?resizew=222)
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名校
2 . 学习几何体结构素描是学习素描的重要一步.如图所示,这是一个用来练习几何体结构素描的石膏几何体,它是由一个圆柱
和一个正三棱锥
穿插而成的对称组合体.棱
和面
与圆柱侧而相切,点
是棱
与圆柱侧而的切点.直线
分别与面
,面
交于点
,圆柱
在面
,面
上分别截得椭圆
.在平面
和平面
中,椭圆
上分别有两组不重合的两点
和
(图中未画出).且满足关系
.已知三棱锥
的外接球表面积为
,圆柱的底面直径为
,请问平面
,平面
上是否分别存在点
,使得对于满足
的直线
分别恒过定点
.若存在,试求
和
夹角的余弦值:若不存在,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/270ddac9587bf1ea553914cb69595ab2.png)
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![](https://img.xkw.com/dksih/QBM/2024/1/13/3410267677220864/3410816027746304/STEM/273256e47234495eaf4d1e8d41ba7a4a.png?resizew=183)
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